In particular in internal combustion engines where the mixture is formed externally, it is known to regulate the combustion air mass flow and hence the charge in the combustion chambers of the internal combustion engine via an actuator provided in the intake tract. Usually this actuator is designed as a throttle plate which can be used to close off the cross-section of the intake tract. The position of the throttle plate then has a direct effect on the charge. If the throttle plate is not fully open, then the air sucked in by the internal combustion engine is throttled and hence the torque output by the internal combustion engine is reduced. This throttle action depends on the position and hence the aperture cross-section of the throttle plate. When the throttle plate is fully open, the maximum torque is output by the internal combustion engine.
To achieve optimum regulation of the throttle plate, the throttle plate is actuated by a positioner having positional feedback; a control device is provided here that calculates the necessary aperture of the throttle plate, taking into account the current operating status of the internal combustion engine, and controls the throttle plate positioner. An accelerator pedal position is evaluated via a pedal transducer for this purpose.
In order to keep the losses occurring at the throttle plate as low as possible, it is known to be able to operate inlet valves of an internal combustion engine with variable valve travel. The inlet valves then open with an adjustable travel path so that, at least in some operating phases of the internal combustion engine, there is no need to actuate the throttle plate. The charge of the internal combustion engine is then regulated exclusively via the adjustment of the valve travel.
In order to achieve both minimum possible consumption and a transition that is as unnoticeable and hence as comfortable as possible between fully unthrottled operation, i.e. operation of the internal combustion engine with charge regulation involving valve travel adjustment, and conventional throttled operation, the aim is for as smooth a transition as possible with overlapping interaction of valve travel regulation and throttle plate regulation.
In this context, a method of the type cited in the introduction is known from DE 199 28 560 A1, wherein a setpoint intake pipe pressure is regulated for the intake pipe by regulating the throttle plate, and the air mass flow is controlled by means of suitable operation of the valve travel adjustment. The generic method involves creating a combination and a transition function of two different torque control systems that can work in all operating conditions. The generic document distinguishes between three operating phases here. In one phase, the air mass flow is regulated exclusively via the valve travel adjustment at a constant pressure setting. In another phase, when the inlet valves are set at maximum valve travel, a further increase in charge is achieved by controlling the throttle plate. In a transition region between these two control processes, throttle plate and valve travel adjustment are controlled in opposition. It is assumed here that the necessary dependencies between valve travel adjustment and pressure differential are known and can be saved in an electronic control unit.
The method described in DE 199 28 560 A1 requires a relatively large amount of memory space, because extensive data records need to be saved for these dependencies and used during the control process in order to implement operation in the transition region.